For example, as a shower device in a bath room, there has been generally used a type of shower device with the hot water having an appropriate temperature being sprayed from a shower head connected to a hot and cold water mixing valve by means of a hose. In such shower device, the temperature of sprayed water is set by adjusting the valve opening degree at the cold water side and hot water side of the hot and cold water mixing valve by means of a wide variety of mechanisms.
In the operation of a shower, the case has actually occurred where the temperature of sprayed water becomes higher and lower than the set value due to a sudden change in the supply pressure of the cold water and hot water and some other causes. In this case, since the sprayed water has an extremely high temperature, some danger is involved, and so provision of a temperature-actuated valve is effective, such valve being so constituted that, if the temperature of hot water which flows toward the shower head exceeds a certain level, the supply of such hot water is shut-off.
Such temperature-actuated valve is described, for example, in JPB Hei-3-64751, the outline of which is shown in FIG. 50.
This temperature-actuated valve comprises a valve seat 251 incorporated into the internal flow passage of a body 250, a lift valve type of valve body 252 which is adapted to be brought into a seating engagement with the valve seat 251, and a damper spring 253 and a coil spring 254 made of a shape-memory alloy arranged so as to hold therebetween a shift ring 252a provided on the valve body 252.
The coil spring 254 maintains a contracted shape up to a certain temperature, so that the valve body 252 is maintained in the position where it is shifted downward in the drawing, and the seating surface of the valve body 252 is brought out of engagement with the valve seat 251 to thereby open the flow passage. When the temperature exceeds a certain temperature, the coil spring 254 expands due to its shape-memory property and the valve body 252 is brought into a seating engagement with the valve seat 251 to close the flow passage, so that supply of the hot water having a high temperature is shut-off.
Further, there is another construction described, for example, in JPU Sho-61-41500, in which a valve body is provided in the direction of traversing the section of a flow passage, and a coil-like temperature sensing expansion body made of a shape-memory alloy is linked coaxially to the moving direction of the valve body. When the temperature of hot water passing therethrough exceeds the set temperature (for example, 50 degrees centigrade), the valve body is shifted due to the coil-like temperature sensing expansion body to thereby close the flow passage.
The lift valve type of valve body 252 has a considerably large flow resistance, since the valve is closed in a way to gradually narrow the flow passage between the valve body 252 and the valve seat 251. This requires an elastic reaction force of the coil spring 254 made of a shape-memory alloy to be made large, in order that the coil spring 254 shifts the valve body 252 in the direction of closing the valve body 252.
However, although the elastic reaction force of the coil spring 254 depends on the quality of material and the heat treatment of a wire rod, it is also proportional to the size of the outer diameter of the wire rod and, therefore, in order to drive the valve body 252 of the above-described lift valve type, it is necessary to make the wire rod of the coil spring 254 thick. If the coil spring 254 is made large in this way, an influence on the aspect of cost cannot be ignored because the raw material thereof is an expensive shape-memory alloy.
Moreover, if the outer diameter of the wire rod of the coil spring 254 is great, the distance between the winding loops of the coil becomes small. Since the hot water flows to the downstream side passing from the outside of the coil spring 254 through the inside thereof, the resistance of the flow passage becomes large. Accordingly, a quantity of the flow is also limited, and if one attempts to ensure the quantity of flow, it is necessary to make the whole valve large in size.
In the valve body 252 of the lift valve type, since the position thereof is held by the elastic support of the spring, when the flow rate and pressure of hot water is large, the position of the valve body 252 is apt to be changed by a change in the flow pressure of hot water. For this reason, a degree of opening the flow passage by the valve body 252 changes, so that the hot water which is discharged also changes in temperature, and providing the operation of the valve body at a stable temperature is limited to equipment with a low flow rate.
Further, also in the device described in JPU Sho-61-41500, since the valve body disposed in the direction of traversing the section of the flow passage is elastically supported by the spring, in the case where the flow rate and pressure of hot water are large, the temperature of hot water changes in a similar way. Moreover, since it is necessary to make the section of the flow passage great to some degree in order to ensure the quantity of hot water supplied, the stroke of movement of the valve body becomes great. For this reason, even though the temperature sensing expansion spring is actuated when the hot water at a high temperature passes, time is consumed until the valve body shuts off the flow passage and, therefore, there is an aspect of this device which is not suitable for instantaneous shut-off of the hot water at a high temperature.
In the meantime, in the case where the temperature-actuated valve is incorporated into a flow passage toward the shower head connected to a hot and cold water mixing valve by means of a hose, it is most preferable to sense the temperature of the hot water immediately after leaving the mixing valve to thereby shut off the flow passage. For this reason, it has been considered that the temperature-actuated valve should be incorporated utilizing such a joint as an elbow which is connected to the back of the hot and cold water mixing valve and to which the base end of the hose is connected.
However, in the device in which the lift valve type of valve body or the valve body of the type of traversing the section of flow passage is incorporated, as described in the above-described publications, the springs in the inner flow passage and the spring which performs the temperature sensing movement are apt to be bulky and, therefore, such spring is not appropriate for incorporation into such elbow.
Further, in order to allow the valve body to be quickly set to the valve closing position as the hot water at a high temperature passes, there is also a device equipped with such a pilot valve mechanism as described, for example, in U.S. Pat. No. 5,295,554. This is a mechanism which comprises a leaf spring made of a shape-memory alloy incorporated into a pilot valve which provides an energizing force to a diaphragm-type main valve in the valve opening direction, and when a small quantity of hot water which passes through the pilot valve reaches a high temperature, the diaphragm-type main valve is closed.
However, in the device including the pilot valve which links the diaphragm, the number of the components is considerably increased and the resistance of the flow passage is great and, in addition, the diaphragm is provided as a main valve, so a loss in pressure is increased. Further, there is a problem in that since the diaphragm is closed due to a difference in pressure before and after the throttling portion of the diaphragm part, in the case where a quantity of flow is small which makes the production of such difference in pressure difficult, it is difficult to discharge the functions as a temperature-actuated valve. Therefore, there is a tendency of the large-sized device similar to that described in the above-described publications to ensure the quantity of flow; so, the position where the diaphragm is incorporated is limited. Moreover, there is a problem in that because of a great loss in pressure, a sufficient delivery quantity of shower water cannot be ensured in a region where water pressure is low.
As described above, the conventional temperature-actuated valve has disadvantages not only in that the flow resistance due to the spring incorporated as a shape-memory element is great and the construction becomes bulky, but also in that the delivery of hot water due to the delay in the valve closing time of the valve body as the hot water at a high temperature passes cannot be avoided.
Moreover, as an example of the hot and cold water mixing valves equipped in a bath room, there is a mixing valve to which a shower head is connected by way of a hose, in addition to a delivery pipe for the supply of cold and hot water to a bathtub. Such hot and cold water mixing valve is normally provided with a switching valve for switching the flow passage to the delivery pipe side or the shower head side, in addition to the valve for adjusting the flow rate and temperature of the mixed water. For example, a switching valve such as that described in JPU Sho-56-32679 is adopted.
This switching valve includes an operating handle to which a cylindrical valve body is linked by way of a torsion spring and, during normal operation, the state is maintained in which the hollow portion of a valve body communicates with the flow passage at the delivery pipe side and, simultaneously, the flow passage toward the shower side is shut off. When the handle is switched to the shower side, the valve body is pressed against the valve seat, which forms the beginning end of the flow passage of the delivery pipe side, by the water pressure of the mixed water toward the shower side, whereby the position of the valve body is suppressed so as to shut off the flow passage toward the delivery pipe.
With such a switching valve, when supply of the mixed water is stopped after switching to the shower side and being used, the water pressure of the mixed water against the valve body gradually drops and, accordingly, the valve body is rotated together with the handle by means of the torsion spring to open the flow passage toward the delivery pipe side and to close the flow passage toward the shower side. Therefore, after the shower has been used, the flow passage is always automatically switched to the delivery pipe side, and even though the switched position remains unconfirmed when the mixing valve is used next time, the delivery of hot water at a high temperature from the shower can be avoided, allowing the mixing valve to be used safely without getting scalded.
In this way, so long as the operation of switching to the shower side is not made by means of the operating handle when the hot and cold water mixing valve is used, the hot water at a high temperature is never discharged from the shower, so this type of the mixing valve is used particularly suitable as equipment for general use.
However, when a user has switched the switching handle to the shower side by mistake at the time the mixing valve begins to be used, he may be suddenly showered with hot water at a high temperature from the shower. Namely, even though hot water is discharged when the delivery pipe is used, the hot water pours only onto a finger tip and there is little hinderance to ease of use. However, if it is a sprayed water from the shower head, the hot water pours over the whole body and, therefore, a degree of danger cannot be ignored for the user who is unfamiliar with the operation.
In this way, even though the switching valve in which the flow passage is switched to the delivery pipe side at the time the mixing valve begins to be used, the case even occurs where the hot water at a high temperature is suddenly discharged when the user makes a mistake in the operation. For this reason, even though the flow passage is switched to the shower side when the mixed water is at a high temperature, it is more preferable from the point of safety to attempt to provide equipment from which the mixed water is not discharged.